Method for producing a coated packaging material

ABSTRACT

The disclosure relates to a method for producing a coated packaging material, in particular a laminate, wherein at least the following steps are carried out: a) providing a cellulose-containing substrate, b) coating at least one surface region of the substrate with a curable composition and curing the composition, forming a primer layer, and c) generating a metal-containing layer on at least one surface region of the primer layer. According to the disclosure, the composition used in step b) contains at least one ionically polymerizable monomer that is cured via ionic polymerization. The disclosure also relates to a packaging material including a cellulose-containing substrate having a layer system, wherein the layer system has at least one primer layer and a metal-containing layer, wherein the primer layer includes/is at least one polymer cured via ionic polymerization, and a packaging produced from at least one packaging material of this type.

The invention relates to a method for producing a coated packagingmaterial, to a coated packaging material, and to a package comprisingsuch a packaging material.

Metal-coated, cellulose-based packaging materials are useful in amultiplicity of applications. For example, metal-coated papers and cardsare suitable for producing gift paper, packaging cartons, and othertypes of packaging. Further known applications are the use of suchpackaging materials for product identification in tobacco products,labels, cases, cosmetic packaging, lottery slips, and the like. In theseapplications, the metal-coated packaging material is generally printedwith a brand identifier, a decorative design and the like, and may havevarious levels of gloss and/or other performance features. A desire inparticular is for metal-coated packaging materials to have a very highlyreflective, lustrous surface. Untreated cellulose-based substrates,however, normally have a relatively irregular surface, meaning thatmetals or metal particles applied directly do not have any regularorientation and cause incoherent scattering and reflection of incidentlight, resulting in a matte surface appearance. Customarily, therefore,a priming coat is first applied to the cellulose-containing substrate,and the metal-containing layer is generated subsequently on said coat.WO 2013/134359 A1, for example, discloses the production of priming coatlayers from acrylates which are polymerized radically by UV or electronbeams (Electron Beam Curing).

Regarded as a disadvantage of the known priming coats, however, is thefact that on curing they experience comparatively severe contraction,resulting in poor adhesion of the priming coat and hence of the metalliclayer on the substrate. Furthermore, priming coats frequently comprisehigh-opacity color and effect systems as well, meaning that the UV lightused for curing cannot penetrate down to the substrate, a phenomenonwhich may likewise result in incomplete through-curing. Moreover,radical polymerizations wherein the active species is a molecule havingan unpaired electron are difficult to control and are inhibited byoxygen; this, without the expensive and complicated use of inert gasesand protective rooms, may likewise result in incomplete and non-uniformdegrees of polymerization and in ready detachment of the priming coat.

It is an object of the present invention to improve a generic method forproducing a coated packaging material in such a way that it is possibleto produce a priming coat having improved adhesion tocellulose-containing substrates. Further objects of the presentinvention are to specify a coated packaging material which has a primingcoat with improved adhesion on a cellulose-containing substrate of thepackaging material, and to specify a package which consists at leastpartly of such a packaging material.

The objects are achieved in accordance with the invention by a methodhaving the features of claim 1, by a packaging material having thefeatures of claim 14, and by a package as claimed in claim 15.Advantageous embodiments with useful developments of the invention areindicated in the respective dependent claims; advantageous embodimentsof each aspect of the invention should be seen as being advantageousembodiments of each other aspect of the invention, and vice versa.

The first aspect of the invention relates to a method for producing acoated packaging material that involves carrying out at least the stepsof a) providing a cellulose-containing substrate, b) coating at leastone surface region of the substrate with a curable composition andcuring the composition to form a priming coat, and c) generating ametal-containing layer on at least one surface region of the primingcoat.

Improved adhesion of the priming coat on the cellulose-containingsubstrate is achieved in accordance with the invention by virtue of thecomposition used in step b) comprising at least one ionicallypolymerizable monomer which is cured by ionic polymerization. Incontradistinction to radical polymerization, the reaction in the case ofionic polymerization is initiated and carried by ions. Like radicalpolymerization, ionic polymerization may be broken down into the foursteps of initiation, growth, chain transfer and termination. Theinvention is based on the finding that the contraction of a priming coatproduced by ionic polymerization is substantially less than in the caseof one produced by radical polymerization, and is typically below 5%,more particularly below 3%. As a result, the priming coat produced inaccordance with the invention possesses particularly good adhesion onthe cellulose-containing substrate. Furthermore, ions as carriers of thepolymerization reaction are substantially more long-lived than radicals,react very selectively and are relatively insensitive toward oxygen,meaning that the polymerization can be carried out without an inert gasatmosphere and, after initiation, may even advance continuously in thedark, thus ensuring through-curing down to the substrate even in thecase of strongly colored and particularly thick priming coats. Moreover,ionic polymerization allows the production of very flexible primingcoats with a correspondingly low tendency to fracture, a particularadvantage when using the packaging materials produced in accordance withthe invention to produce packages. Fluting, stamping and embossing, andalso microembossments, especially, require a highly flexible base and ahighly flexible priming coat, respectively. In contrast to compositionswhich polymerize radically, moreover, compositions which polymerizeionically can be formulated to be at least approximately odorless and/oremission-free, and, after polymerization, lead to priming coat layerswhich are also low in emissions or emission-free, resulting in asignificantly lower hazard potential and nuisance potential for theprocessor during production. There is also, advantageously, no need forcomplex and expensive inert gas or air removal units. Further advantageslie in the possibility of generating highly lustrous metal-containinglayers on the priming coat produced in accordance with the invention,since this priming coat, owing to the uniform progress of reaction fromthe surface in the direction of the substrate in the course of curing,forms a correspondingly uniform and readily coatable surface for themetal-containing layer, with unevennesses in the substrate surface beingleveled automatically. The cellulose-containing substrate may inprinciple be uncoated or may already have been coated with one or morelayers, with an uncoated substrate being preferred. For example, thesubstrate may be coated or uncoated paper, coated or uncoated card, orcoated or uncoated board.

In one advantageous embodiment of the invention the composition used instep b) is cured anionically or cationically and/or by living ionicpolymerization. In an anionic polymerization, the active species areanions. Anionic polymerization takes place preferably in the case ofmonomers having electron-withdrawing (−M effect) substituents such asnitrile, carboxyl, phenyl and vinyl groups. In a cationicpolymerization, the active species are cations. Cationic polymerizationtakes place preferably in the case of monomers having electron-donating(+M effect) substituents and proceeds in general by way of carbenium,oxonium, ammonium ions and the like. In the absence of terminationreactions, the anions or cations are retained even after completereaction of the monomer, and so the charged polymers, following additionof further monomers, are able to continue their chain growth, bringingabout the possibility of what is called living polymerization. By thismeans, advantageously, covalent attachment of the metal-containing layerto the priming coat is made possible, if the metal-containing coat islikewise produced using a formulation having corresponding ionicallypolymerizable monomers, in the form of a metal-containing paint ormetal-containing ink, for example, with the metal-containing layerthereby adhering to the priming coat in a particularly reliable way.Another possibility, as and when required, is also to first generate asecond priming coat layer or functional layer on the first priming coat,before the metal-containing layer is generated.

In a further advantageous embodiment of the invention, the compositionused in step b) is cured by means of an initiator, more particularly apreferably blocked compound from the group of the Lewis and/or Brønstedacids and/or the Lewis and/or Brønsted bases, and/or by thermal and/orphotochemical activation. With the aid of an initiator, thepolymerization reaction can on the one hand be initiated in a controlledway and can on the other hand be adjusted in relation to the desiredchain-length distribution. The initiator may in principle be addeddirectly or may form only by reaction with the monomer. In the case of acationic polymerization, Lewis acids can be used that initiate thecationic polymerization even at low temperatures. The resulting polymerspossess a relatively high molar mass. Examples of those which can beused, individually and in any desired combination, are metal halidessuch as BF₃, SnCl₄, SbCl₅, ZnCl₂, TiCl₄, PCl₅ and AlCl₃, oxyhalides suchas POCl₃, CrO₂Cl, SOCl₂, VOCl₃ and the like, trityl chloride, and alsoorganometallic compounds such as RAlCl₂, R₂AlCl, R₃Al orbenzyl(tetrahydrothiophenium) hexafluoroantimonate. The initiation ofthe polymerization using Lewis acids may be promoted via the presence ofa proton donor such as water, alcohol, or an organic acid. Accordingly,the reaction can also be carried out in the presence of atmosphericmoisture, moisture in the substrate, etc. Brønsted acids are able toinitiate the reaction by protonating the monomer. The acid used oughtgenerally to be strong enough to produce a sufficient amount ofprotonated monomers, but ought also not to be too greatly nucleophilic,since otherwise there may be premature termination through a combinationwith the protonated monomer/oligomer/polymer, something which would leadto relatively short chain lengths. Halogen acids are therefore lesspreferable, whereas perchloric, sulfuric, phosphoric, fluorosulfonic,chlorosulfonic, methanesulfonic and trifluoromethanesulfonic acids areparticularly suitable. Brønsted bases and/or Lewis bases may be usedmore particularly for initiating the anionic polymerization. Suitable asinitiators here as well are numerous compounds such as, for example,individually and in any desired composition, metal amides such as(Na/K)NH₂ and LiC₂H₅, alkoxides, hydroxides, cyanides, phosphines,amines, organometallic compounds, especially organolithium compoundssuch as alkyllithium compounds, alkoxides, alkali metals or PhMgBr. Thepolymerization in this case is initiated by the addition of anucleophile onto the monomer. Through the choice of thermal and/orphotochemical activation is it possible to initiate the ionicpolymerization reaction as and when required.

Further advantages arise by selecting the at least one ionicallypolymerizable monomer from a group which encompasses epoxides, moreparticularly the cycloaliphatic epoxides and glycidyl ethers, isoprenes,cyanoacrylates, lactides, caprolactones, caprolactams,alkylcyclotrisiloxanes, vinyl ethers and isobutenes, and/or from a groupwhich encompasses compounds having at least one electron-donatingsubstituent, more particularly one or more alkoxy, phenyl, vinyl and/or1,1-dialkyl groups. By this means it is possible to produce primingcoats having particularly high flexibility, particularly effectiveadhesion to cellulose, high abrasion resistance, high luster, goodhardness, high chemical resistance, and a good barrier effect. Anexample of an epoxide that can be used is3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate(7-oxa-bicyclo[4.1.0]heptan-3-ylmethyl-7-oxa-bicyclo[4.1.0]heptane-3-carboxylate).

In a further advantageous embodiment of the invention the curing in stepb) is carried out at an atmospheric humidity and/or surface humidity ofbetween 5% and 65%. The atmospheric humidity in the context of thepresent invention refers to the relative atmospheric humidity, expressedin percent (%), which for the current temperature and the currentpressure indicates the ratio of the instantaneous water vapor content tothe maximum possible water vapor content in the ambient atmosphere ofthe substrate.

Correspondingly, the surface humidity indicates the relative atmospherichumidity directly at the surface of the substrate to be coated. If thesubstrate is colder than the ambient air, there may be cooling of theair directly at the substrate surface, and consequently the surfacehumidity may in some cases be higher than the (ambient) atmospherichumidity. Values between 5% and 65% are understood more particularly asatmospheric and/or surface humidity values of 5%, 6%, 7%, 8%, 9%, 10%,11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%,25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%,39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%,53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64% or 65%, andalso corresponding values in-between. By this means it is possible toset the properties of the priming coat ideally, since water influencesthe cure rate, the conversion and the degree of crosslinking, and hencethe resulting hardness or flexibility of the priming coat.

Further advantages arise if the composition used in step b) comprises atleast one polyol, more particularly from a group which encompassespolyethylene glycols, polypropylene glycols, polyethylenepropyleneglycols and poly(tetrahydrofuran)dioles. This permits targetedflexibilization of the priming coat.

In a further advantageous embodiment of the invention the compositionused in step b) comprises nanoparticles, more particularly from thegroup of modified and unmodified silica particles. Using nanoparticlesas fillers allows the priming coat to be functionalized specifically, inrelation, for example, to its coloration, contraction on curing,combined toughness and flexibility, and coefficient of thermalexpansion.

In a further advantageous embodiment of the invention the curablecomposition comprises at least one solvent, more particularly a weaklypolar solvent from the group of methylene chloride, toluene, apolarhydrocarbons and tetrahydrofuran. Since ions constitute the activespecies of the polymerization, great influence over the reaction can begained via the solvent or solvent mixture by providing the respectiveions specifically in the form of covalent polymers, a contact ion pair,a solvent-separated ion pair, or free ions. By this means it is possiblein particular to adjust the rate of the polymerization and also theaverage chain length of the polymers and hence the mechanical propertiesof the priming coat.

In a further advantageous embodiment of the invention the ionicpolymerization is terminated by addition of at least one counterionand/or of at least one terminating reagent and/or by backbiting, and/orin that at least one second monomer type is added when the at least onemonomer has reached or exceeded a predetermined degree ofpolymerization. This as well is a simple way of specifically adjustingthe mechanical properties of the priming coat. The ionic polymerizationmay be terminated spontaneously, by combination with the counterionand/or by addition of terminating reagents (water, methanol, etc.). Ifonly the growing chain is terminated, by transfer of protons to amonomer or by backbiting and elimination of a proton, for example, thedegree of polymerization is indeed limited, and yet the polymerizationrate remains at least approximately unchanged. “Backbiting” refers to anintramolecular electrophilic aromatic substitution reaction which ispossible in particular with aromatic monomers, causing the initiatorcomplex to reform. Where at least one second monomer (of different kind)is added, block copolymers can be prepared. In this case it is of coursepossible to add different kinds of monomers in each case when a definedaverage chain length is reached or exceeded, in order to preparedifferent block copolymers from two, three, four or more monomer types.

Further advantages come about if the curable composition is applied tothe substrate by means of a leveling coating process, more particularlyby means of doctor, blade and/or film press and/or by means of a contourcoating process, more particularly by means of casting, spraying,curtain coating and/or airbrush, and/or by a printing process, moreparticularly by planographic printing, gravure printing, digitalprinting, screen printing and/or relief printing. The use of a levelingcoating process allows material to be smoothed and is particularlyuseful insofar as any subsequent non-contact application techniqueslargely retain the contour of the substrate surface. This means that arough surface contour in the base material or the substrate iscompensated and thereby smoothed with the aid of a leveling coatingprocess. Generally speaking, the smoother the web of material, thehigher the product quality achieved. Through the use of leveling orevening-out coating processes it is possible, in summary, to generate aprimer having a particularly smooth surface on rough substrates. Thissmooth surface is then particularly suitable for subsequent generationof the metal-containing layer. The use of contour coating processesoffers the fundamental advantage that no pressure is exerted at thepoint of contact between substrate and composition, thereby preventing(excessively) deep penetration of the composition into the cellulosebase material. Particularly uniform priming coats can be produced bythis means. At the same time, particularly low quantities of compositionare needed for application in order to achieve a desired thickness ofthe priming coat, and so the method can be carried out particularlyeconomically. With the aid of a printing process, the priming coat canbe generated particularly quickly and flexibly on the substrate, and thesurface of the substrate or of the priming coat can be simultaneouslystructured as and when required.

In a further advantageous embodiment of the invention the priming coatis surface-treated before step c). By this means it is possible toimprove the application and the adhesion of the subsequent layer orlayers. For this purpose, for example, the priming coat may beplasma-treated. A further possibility is to provide the priming coatwith a particular visual appeal or to carry out otherfunctionalizations.

In a further embodiment of the invention, the metal-containing layer isproduced by applying and drying and/or curing a metallic paint and/or byphysical and/or chemical vapor deposition, more particularly byorganometallic chemical vapor deposition. This represents a particularlyflexible way of generating the metal-containing layer.

In a further advantageous embodiment of the invention a top layer, whichmore particularly is opaque or transparent, is applied to themetal-containing layer. As well as protecting the metal-containing layerfrom environmental effects, it is also possible by this means toinfluence the visual appeal of the packaging material, as and whenrequired.

A second aspect of the invention relates to a packaging materialcomprising a cellulose-containing substrate with a layer system, saidlayer system comprising at least one priming coat and a metal-containinglayer. Improved adhesion of the priming coat on the cellulose-containingsubstrate of the packaging material is ensured in accordance with theinvention in that the priming coat is or comprises at least one polymercured by ionic polymerization. The invention is based on the findingthat the contraction of a priming coat produced by ionic polymerizationis substantially less than in the case of one produced by radicalpolymerization, and is typically below 5%, more particularly below 3%.As a result, the priming coat possesses particularly good adhesion onthe cellulose-containing substrate. Furthermore, ions as carriers of thepolymerization reaction are substantially more long-lived than radicals,react very selectively and are relatively insensitive toward oxygen,meaning that the polymerization can be carried out without an inert gasatmosphere and, after initiation, may even advance continuously in thedark, thus ensuring through-curing down to the substrate even in thecase of strongly colored and particularly thick priming coats. Moreover,ionic polymerization allows the production of very flexible primingcoats with a correspondingly low tendency to fracture, a particularadvantage when using the packaging material produced in accordance withthe invention to produce packages. Fluting, stamping and embossing, andalso micro embossments, especially, require a highly flexible base and ahighly flexible priming coat, respectively. In contrast to compositionswhich polymerize radically, moreover, compositions which polymerizeionically can be formulated to be at least approximately odorless and/oremission-free, and, after polymerization, lead to priming coat layerswhich are also low in emissions or emission-free, resulting in asignificantly lower hazard potential and nuisance potential for theprocessor during production. There is also, advantageously, no need forcomplex and expensive inert gas or air removal units. Further advantageslie in the possibility of generating highly lustrous metal-containinglayers on the priming coat produced in accordance with the invention,since this priming coat, owing to the uniform progress of reaction fromthe surface in the direction of the substrate in the course of curing,forms a correspondingly uniform and readily coatable surface for themetal-containing layer, with unevenesses in the substrate surface beingleveled automatically. The cellulose-containing substrate may inprinciple be uncoated or may already have been coated with one or morelayers, with an uncoated substrate being preferred. For example, thesubstrate may be coated or uncoated paper, coated or uncoated card, orcoated or uncoated board. The cellulose base material of the substratemay preferably have a mass per unit area of between 5 g/m² and 2000g/m², more particularly between 100 g/m² and 1000 g/m² and morepreferably between 200 g/m² and 800 g/m². This allows the packagingmaterial to be adapted particularly flexibly to different end uses. Ifthe base material has a mass per unit area of between about 5 g/m² andabout 150 g/m², it is referred to in the context of the invention aspaper. Base material having a mass per unit area of between about 150g/m² and about 800 g/m² is referred to in the context of the inventionas card, whereas base material having a mass per unit area of betweenabout 800 g/m² and about 2000 g/m² is referred to as board. In its mostsimple embodiment, the priming coat consists exclusively of theionically polymerized polymer. Alternatively, in addition to theionically polymerized polymer, the priming coat may comprise furthersubstances. Moreover, the substrate may be a laminate. A laminateconsists of one or more layers of paper impregnated in a resin such asphenolic resin or melamine resin and assembled under high pressure. Thetopmost layer of the layer system (finish film) may be an opaque ortransparent top coat (overlay) for protection from mechanical exposure.At least one layer in the layer system may also carry a motif(decorative laminate). It may additionally be the case that thepackaging material is equipped with electrical and/or electroniccomponents and/or energy sources, which are electrically connected toone another by way of the metal-containing layer, in the form ofconductor tracks, optionally (“paper or card circuit board”). Furtherfeatures and their advantages are evident from the descriptions of thefirst aspect of the invention, with advantageous embodiments of thefirst aspect of the invention being regarded as advantageous embodimentsof the second aspect of the invention, and vice versa.

A third aspect of the invention relates to a package which comprises atleast one packaging material obtainable and/or obtained by a methodaccording to the first aspect of the invention and/or which takes a formaccording to the second aspect of the invention. This ensures improvedadhesion of the priming coat on the cellulose-containing substrate ofthe packaging material. The package may take the form, for example, offood packaging, more particularly of packaging for solid foodstuffs, ofpackaging for confectionery, or as beverage packaging for liquidfoodstuffs, as packaging for tobacco products, as gift or surroundpackaging, as carrier packaging, etc.

Further features and their advantages are evident from the descriptionsof the first and second aspects of the invention, with advantageousembodiments of the first and second aspects of the invention beingregarded as advantageous embodiments of the third aspect of theinvention, and vice versa.

Further features of the invention are apparent from the claims, thefigures, and the description of the figures. The features andcombinations of features stated above in the description, and also thefeatures and combinations of features stated below in the description ofthe figures and/or shown in isolation in the figures, can be used notonly in the combination indicated in each case but also in othercombinations, without departing from the scope of the invention.Consequently, the invention should be deemed to embrace and discloseadditionally embodiments that are not explicitly shown and elucidated inthe figures but are apparent from and can be generated by separatecombinations of features from the embodiments that are elucidated. Thedisclosure should also be deemed to encompass embodiments andcombinations of features which, therefore, do not have all of thefeatures of an originally formulated independent claim. Here, the singleFIGURE shows a schematic sectional view from the side of a packagingmaterial of the invention, according to one working example.

The single FIGURE shows a schematic sectional view from the side of apackaging material 10 of the invention, according to one workingexample. The packaging material comprises a substrate 12, which of acellulose-containing base material 14 and comprises an inside 16 facingaway from the packaged contents, and an outside 18 facing away from thepackaged contents. In the present working example, the base material 14comprises uncoated paper having a mass per unit area of about 100 g/m².On the outside 18 of the substrate 12 there is a layer system 20 whichcomprises a priming coat 22, a metal-containing layer 24, and a toplayer 26. To produce the priming coat 22, which in principle may also bereferred to a primer, the substrate 12 was coated with a compositioncontaining a cationically polymerizable monomer which was cured byirradiation with UV light. The monomer used was the cycloaliphatic epoxyresin 7-oxa-bicyclo[4.1.0]heptan-3-ylmethyl7-oxa-bicyclo[4.1.0]heptane-3-carboxylate with the formula

together with a photoinitiator based on antimony hexafluoride and havingthe formula

Alternatively or additionally it is also possible in principle to useother epoxides and/or vinyl resin-based monomers. The cationicpolymerization starts by opening of the epoxide rings, and brings aboutongoing chain growth. The contraction during the polymerization was inthis case at most 3%, meaning that adhesion of the substrate 12 wasexcellent. Because of the insensitivity of the cationic polymerizationtoward oxygen, it was possible to carry out the reaction without aprotective gas atmosphere. The atmospheric humidity was set at about30%. In addition, even prior to the UV irradiation, the composition washeated to a temperature of about 45° C. or more by means of an infraredheat source in order to achieve an increase in the reaction rate. Thetemperature of the substrate 12 was held at not less than 40° C. untilthe end of the polymerization, in order to ensure completethrough-curing of the priming coat 22. As well as very good flexibility,the priming coat 22 also possesses high abrasion resistance and also avery high luster owing to the uniform surface, thereby considerablyboosting not only the adhesion but also the luster and the reflection ofthe metal-containing layer 24 applied subsequently. The composition forthe priming coat 22, the metal-containing layer 24, and the concluding,fundamentally optional top layer 26 were each applied by printing. Toproduce the metal-containing layer 24, a conventional metallic paint wasapplied and cured. An alternative option is for the metallic paint aswell to comprise an ionically polymerizable monomer as curing agent,allowing covalent attachment to the priming coat 22, optionally. The toplayer 26 consists of a transparent clearcoat varnish, and protects theunderlying layers of the layer system 20 from environmental effects.

It will be appreciated that the layer system 20 may also be generatedonly on the inside 16 or both on the inside 16 and on the outside 18. Inthat case, moreover, layer systems 20 generated on the inside 16 and onthe outside 18 may be alike or different.

The parameter values reported in the documents for the definition ofprocess conditions and measurement conditions for the characterizationof specific properties of the subject matter of the invention should beregarded as being encompassed by the scope of the invention even withinthe scope of deviations—resulting, for example, from measurement errors,system errors, weighing errors, DIN tolerances and the like.

1. A method for producing a coated packaging material, more particularlya laminate, comprising at least the steps of: a) providing acellulose-containing substrate; b) coating at least one surface regionof the substrate with a curable composition and curing the compositionto form a priming coat; and c) generating a metal-containing layer on atleast one surface region of the priming coat; wherein the compositionused in step b) comprises at least one ionically polymerizable monomerwhich is cured by ionic polymerization.
 2. The method as claimed inclaim 1, wherein the composition used in step b) is cured anionically orcationically and/or by living ionic polymerization.
 3. The method asclaimed in claim 1, wherein the composition used in step b) is cured bymeans of an initiator, more particularly a preferably blocked compoundfrom the group of the Lewis and/or Brønsted acids and/or the Lewisand/or Brønsted bases, and/or by thermal and/or photochemicalactivation.
 4. The method as claimed in claim 1, wherein the at leastone ionically polymerizable monomer is selected from a group whichencompasses epoxides, more particularly the cycloaliphatic epoxides andglycidyl ethers, isoprenes, cyanoacrylates, lactides, caprolactones,caprolactams, alkylcyclotrisiloxanes, vinyl ethers and isobutenes,and/or from a group which encompasses compounds having at least oneelectron-donating substituent, more particularly one or more alkoxy,phenyl, vinyl and/or 1,1-dialkyl groups.
 5. The method as claimed inclaim 1, wherein the curing in step b) is carried out at an atmospherichumidity and/or surface humidity of between 5% and 65%.
 6. The method asclaimed in claim 1, wherein the composition used in step b) comprises atleast one polyol, more particularly from a group which encompassespolyethylene glycols, polypropylene glycols, polyethylene-propyleneglycols and poly(tetrahydrofuran)diols.
 7. The method as claimed inclaim 1, wherein the composition used in step b) comprisesnanoparticles, more particularly from the group of modified andunmodified silica particles.
 8. The method as claimed in claim 1,wherein the curable composition comprises at least one solvent, moreparticularly a weakly polar solvent from the group of methylenechloride, toluene, apolar hydrocarbons, and tetrahydrofuran.
 9. Themethod as claimed in claim 1, wherein the ionic polymerization isterminated by addition of at least one counterion and/or of at least oneterminating reagent and/or by backbiting, and/or in that at least onesecond monomer type is added when the at least one monomer has reachedor exceeded a predetermined degree of polymerization.
 10. The method asclaimed in claim 1, wherein the curable composition is applied to thesubstrate by means of a leveling coating process, more particularly bymeans of doctor, blade and/or film press and/or by means of a contourcoating process, more particularly by means of casting, spraying,curtain coating and/or airbrush, and/or by a printing process, moreparticularly by planographic printing, gravure printing, digitalprinting, screen printing and/or relief printing.
 11. The method asclaimed in claim 1, wherein the priming coat is surface-treated beforestep c).
 12. The method as claimed in claim 1, wherein themetal-containing layer is produced by applying and drying and/or curinga metallic paint and/or by physical and/or chemical vapor deposition,more particularly by organometallic chemical vapor deposition.
 13. Themethod as claimed in claim 1, wherein a top layer, which moreparticularly is opaque or transparent, is applied to themetal-containing layer.
 14. A packaging material comprising acellulose-containing substrate having a layer system, said layer systemcomprising at least one priming coat and a metal-containing layer,wherein the priming coat is or comprises at least one polymer cured bybionic polymerization.
 15. A package which comprises at least onepackaging material which is obtainable and/or obtained by a method asclaimed in claim
 1. 16. A package which comprises at least one packagingmaterial that takes the form as claimed in claim 14.